Campylobacter species are recognised as the most frequent cause of bacterial gastroenteritis in the United Kingdom and many other countries throughout the world. In the U.K. approximately 90% and 10% of case isolates are identified as Campylobacter jejuni and Campylobacter coli respectively, plus a small number of other species such as Campylobacter upsaliensis and lari. The majority of the infections are sporadic the source of which remains largely unknown although the importance of several vehicles is now recognised.
There is a known desire to be able to detect and differentiate species of Campylobacter. However, it is also known that present Campylobacter enrichment culture techniques lack sensitivity, making detection difficult. Campylobacter jejuni does not multiply in foodstuffs and low numbers may be present together with a high background of indigenous microflora. Also, surface viable counts of Campylobacter can decrease rapidly and cells that are potentially culturable are often lost before samples reach a laboratory for analysis. Another factor making detection problematic is that antibiotics used in culture enrichment media may damage already weakened Campylobacter.
There are currently available assays for detection of a variety of food and water-borne pathogens; L. pneumophila, V. vulnificus, enteroinvasive E. coli, Shigella; but no satisfactory method of detecting Campylobacter or distinguishing between the four main Campylobacter species is known.
A method of detecting Campylobacter has been published by Giesendorf, B A J, et al in Applied and Environmental Microbiology, December 1992, pages 3804-3808. The method detects the species jejuni, coli and lari, and produces similar results to conventional methods but in a reduced time. The method suffers from a number of drawbacks. It does not enable detection of the species upsaliensis. Further, the method employs polymerase chain reaction (PCR) techniques but nevertheless requires a short enrichment culture before the PCR can be employed. Further still, the primer used for the PCR does not have the precise homology with DNA sequences in the three Campylobacter species that can be detected using the method.
Another method for detecting Campylobacter jejuni and Campylobacter coli is known from Wegmuller, B E et al, Applied Environmental Microbiology, vol. 59, part 7, 1993 pages 2161-2165. The described method detects only the species jejuni and coli.
In addition to the above-identified problems with detection and speciation of Campylobacter, recent work on Campylobacter jejuni suggests that in certain circumstances it enters a "non-culturable, viable form" when subjected to environmental stresses, such as pH or temperature extremes, increased oxygen tension or nutrient depletion. In this form, Campylobacter infectivity is maintained but-the organisms cannot be cultured. Thus there exists a need for the improvement of methods of detection of non-culturable forms of Campylobacter.